HABITS OF A D 10 DON 



13 



the limits of the tidal waves ; and as the rivulet slowly trickles 

 down, the surf must supply the polishing power of the cataracts 

 in the great rivers. In like manner, the rise and fall of the tide 

 probably answer to the periodical inundations ; and thus the 

 same effects are produced under apparently different but really 

 similar circumstances. The origin, however, of these coatings 

 of metallic oxides, which seem as if cemented to the rocks, is not 

 understood ; and no reason, I believe, can be assigned for their 

 thickness remainingr the same. 





DIODON MACULATUS (DISTENDED AND CONTRACTED). 



One day I was amused by watching the habits of the Diodon 

 antennatus, which was caught swimming near the shore. This 

 fish, with its flabby skin, is well known to possess the singular 

 power of distending itself into a nearly spherical form. After 

 having been taken out of water for a short time, and then 

 again immersed in it, a considerable quantity both of water and 

 air is absorbed by the mouth, and perhaps likewise by the 

 branchial orifices. This process is effected by two methods : the 

 air is swallowed, and is then forced into the cavity of the body, its 



